Journal of Neurology, Neurosurgery, and Psychiatry 199 1;54:793-802 793 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.9.793 on 1 September 1991. Downloaded from The prognosis of hospital-referred transient ischaemic attacks Graeme J Hankey, James M Slattery, Charles P Warlow Abstract because most patients with TIA receive some A cohort of 469 hospital-referred form of treatment (for example, antihyperten- patients with transient ischaemic attacks sive, antiplatelet, anticoagulant, carotid endar- (TIA) of the brain (66%) or eye (34%) terectomy) which influences outcome, whilst due to presumed atheromatous throm- other patients have never reported, nor per- boembolism, lipohyalinosis or car- haps even noticed, such transient symptoms. diogenic embolism, without prior stroke, The prognosis of TIA, describing the out- was assembled between 1976-86. Follow come of TIA patients who have come under up was prospective and complete until medical care and who have been treated in a the patients death or the end of 1986. variety of ways that may have affected the During a mean period of follow up of 4-1 subsequent course of events, has been the years there were 82 deaths (58 vascular, subject of several studies with differing meth- 24 non-vascular), 63 first-ever strokes and ods and results.'-9 The sources of variation 58 patients with coronary events. A include: a) the population (patient sample) coronary event accounted for 51% of examined: this may be community57 101119 or deaths whilst stroke was the cause in hospital-based,"6 12-18 with differences in 12%. The average risk of death over the referral patterns, patient selection, age struc- first five years after TIA was 4 5% per ture, the presence and level of vascular dis- year. The risk of stroke was 6-6% in the eases and risk factors, and the presence'4 '5 or first year and 3 4% per year on average absence""'52 of a history of previous stroke; over the first five years. Stroke occurred b) the size of the sample: many studies are in the same vascular territory as the limited by small numbers""3 and conse- initial TIA in about two-thirds of cases, quently estimates of prognosis have wide con- and was of lacunar type in one fifth of fidence intervals; c) the definition ofTIA: some these strokes. The average risk of a studies have only included patients with TIA coronary event over the first five years symptoms of one hour4 or four hours3 dura- after TIA was 3-1% per year, similar to tion while other studies have included patients that of stroke. However, the risk of a with symptoms lasting up to 72 hours and coronary event, and also death, was others have excluded patients with symptoms fairly constant each year after a TIA, in lasting less than 15 minutes;6 some studies contrast to the risk of stroke which was have examined only patients with their first highest in the first year. The average risk TIA55 1013 or an "incident" TIA,19 whereas of stroke, myocardial infarction or vas- others have studied patients who presented http://jnnp.bmj.com/ cular death over the first five years after with a TIA, whether or not it is their first, and TIA was 6-5% per year and the average some studies have even included patients with risk of stroke, myocardial infarction or merely non-focal symptoms;' d) methodology: death from any cause was 7 5% per year. prospective cohort study2 4 6 7 9 11 14 15 17-19 or The prognosis of this cohort of hospital- retrospective case series study;' 3 5 8 10 12 13 16 e) referred TIA patients was better than treatment: various medical and/or surgical that of TIA in the same com- treatments; definition and assessment of out- patients f) on September 27, 2021 by guest. Protected copyright. munity who presented to the Oxford- come events, such as stroke; g) length and shire Community Stroke Project adequacy of follow up; and h) analysis: many (OCSP), and reflected the impact of studies have expressed the outcome of TIA referral bias. The hospital-referred patients in very simple terms: the number of patients were younger, assessed at a later deaths or strokes occurring during the average date after their last TIA, and comprised period of follow up divided by the original Department of Clinical a greater proportion of patients who had total number of patients. This method fails to Neurosciences, had a TIA of the eye (amaurosis fugax), consider the timing of the event, such as Western General which had a better prognosis than TIA of stroke, during follow up (for example, it does Hospital, Edinburgh, UK the brain. Knowledge of the prognosis of not distinguish between a stroke occurring G J Hankey different populations of TIA patients not within five days of a TIA from a stroke occur- J M Slattery only enhances understanding and inter- ring five years later) nor the outcome of C P Warlow pretation of previous studies but is also patients who were "lost" to follow up or who Correspondence to: for man- died, for example, from other perhaps more Dr Hankey, Department of required optimal patient Clinical Neurosciencies, agement and the planning of treatment frequent causes (such as cardiac deaths), and Western General Hospital, trials. who were therefore no longer at risk of stroke. Crewe Road, Edinburgh, UK The actuarial life table20 and Kaplan-Meier Received 19 July 1990 and in The natural history of transient ischaemic product limit2' techniques both allow for cen- final revised version sored data and very similar 21 December 1990. attacks of the brain and eye (TIA), without generally produce Accepted 17 January 1991. medical intervention, is unknown. This is survival curve estimates. Given the differences 794 Hankey, Slattery, Warlow J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.54.9.793 on 1 September 1991. Downloaded from in duration and adequacy of follow up hospital consultant in 19%. Standard diagnos- amongst the studies, it is almost impossible to tic and outcome criteria (appendix) were compare the results of studies which did not applied and patients who were considered to use actuarial methods of analysis. have a diagnosis ofmigraine, epilepsy or trans- Furthermore, although TIAs (and some of ient global amnesia were excluded. Complete the outcome events, such as stroke) have follow up was achieved by way ofeither regular usually been studied as a homogeneous group, clinical review at four to 12 monthly intervals they are heterogeneous in many respects, such until the patient died or the end of 1986 as pathogenesis (for example, TIA due to (n = 467), or by writing to the patient and/or hyperviscosity or arteritis, as opposed to the general practitioner (n = 14). All patients thromboembolism). It is likely that TIAs of who had a vascular event of any consequence different pathogenesis also have a different were evaluated by CPW and all available prognosis. records, including necropsy reports, were re- Not only is it difficult to compare the results viewed. A second observer (GJH) reviewed the of many of the previous studies of TIA prog- records at the end of the study. nosis (particularly those with few cases, Cerebral angiography was carried out if a inadequate follow up and without actuarial patient was a potential candidate for carotid analysis of the survival data) but reports of endarterectomy on clinical grounds (that is, TIA prognosis from different periods, even carotid TIA and medically fit for surgery) and within the same medical institution, may not had consented to surgery if the angiogram be comparable.22 showed a potentially operable lesion of the The only published prospective and com- internal carotid artery (ICA). The decision to munity-based study of the prognosis of TIA proceed to cerebral angiography was not which had enough patients to provide a influenced by the presence or absence of a reasonable estimate of prognosis was carried carotid bruit. Non-invasive carotid ultrasound out in Oxfordshire, United Kingdom between studies were not available to screen and select 1981-86.'9 During a similar period (1976-86), patients for angiography. and in the same community, one of us (CPW) prospectively evaluated and followed up a Statistical analysis large hospital-referred series of patients with Survival analysis of the TIA population was TIA. Standardised diagnostic and outcome confined to 469 of the 481 patients (98%) in criteria were applied prospectively in both whom the cause of the presenting TIA was populations and all outcome events were considered to be atheromatous arterial throm- analysed using actuarial methods. It is bosis, causing thromboembolism or haemo- therefore possible to compare and contrast the dynamic compromise, lipohyalinosis or car- prognosis of TIA patients who are seen by a diogenic embolism. Eight patients with general practitioner in the comunity with the arteritis, three patients with focal cerebral prognosis of TIA patients who are seen in a ischaemia caused by cardiac arrhythmia and hospital by a consultant neurologist, and to one patient with carnio-cervical trauma were study the influence of referral bias on the excluded from the survival analysis. results. Neurological consultation with CPW was taken This series is a descriptive account of prog- as day 0 of follow up. As this is a study of nosis. Later, we shall be reporting on which prognosis and not untreated natural history, we http://jnnp.bmj.com/ baseline variables, such as hypertension, have included all patients, whether treated angiographic evidence of carotid stenoses, (with aspirin, carotid surgery, etc) or not. The affect prognosis. We shall also be reporting a Kaplan-Meier technique of survival analysis predictive model of prognosis that has been was used.2' The average annual risk (z%) of derived from the important prognostic factors each outcome event was calculated as follows: in these hospital-referred patients which may z = 100 [1 - (1 - y/I00)"/5)%, where y = apply to other TIA populations.